The Washington University Small Animal Imaging Resource (WUSAIR), one of the five original Small Animal Imaging Resource Program (SAIRP) centers funded in 1999, provides state-of-the-art facilities and infrastructure for MRI, PET, CT and optical imaging of mice, rats and other small laboratory animals. Located in the heart of the Washington University Medical Center, WUSAIR combines instrumental and intellectual capabilities found at few other institutions. WUSAIR serves a broad community of cancer scientists, non-expert in MRI, CT, PET or optical technology, who have a pressing need for quantitative image analysis of small laboratory animal model systems. A particular focus is on mouse and rat models of cancer. WUSAIR also provides research and development at the frontier of imaging technology in an effort to make the most powerful new imaging strategies available to its community of users. The ancillary services and capabilities within WUSAIR include physics and engineering support for the development and design of new hardware and imaging methods; informatics support for local and remote data access, analysis, visualization and archival; new contrast agent development; biostatistics consultation for experiment planning and data analysis; and animal procedure assistance for surgical procedures, catheter placement and maintenance and monitoring of physiologic status during imaging experiments. In addition to providing access to and maintenance of MRI, PET, CT and optical small animal scanners and ancillary facilities, WUSAIR services include assistance and training of researchers in small animal imaging procedures and data analysis. Importantly, WUSAIR is intended to bring imaging expertise fully into the cancer research community by encouraging individuals in collaborating research groups to become competent in hands-on small animal imaging methods. Providing a training center for small animal cancer imaging science extends the impact of WUSAIR beyond that of simply providing imaging services. This training program includes support for a yearly advanced imaging symposium, introductory teaching sessions for local researchers, and technology transfer through multiple-day exchanges of imaging scientists between WUSAIR and other centers of imaging excellence. [unreadable] [unreadable]